/*
author:jxy
lang:C/C++
university:China,Xidian University
**If you need to reprint,please indicate the source**
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#define INF 1E9
using namespace std;
double v[1010];
int num[1010],q[1010];
bool cmp(int a,int b)
{
    return v[a]/num[a]>v[b]/num[b];
}
int ff[1010],ss[1010],fa[1010];
int n,r,val[1010];
int farther(int i)
{
    if(ff[i]==i)return i;
    return ff[i]=farther(ff[i]);
}
int son(int i)
{
    if(ss[i]==i)return i;
    return son(ss[i]);
}
bool input()
{
    scanf("%d%d",&n,&r);
    if(n==0&&r==0)return 0;
    int i,f,s;
    r--;
    for(i=0;i<n;i++)
    {
        scanf("%d",&val[i]);
        fa[i]=ff[i]=ss[i]=q[i]=i;
        num[i]=1;v[i]=val[i]*1.0;
    }
    for(i=1;i<n;i++)
    {
        scanf("%d%d",&f,&s);
        fa[s-1]=f-1;
    }
    return 1;
}
void solve()
{
    int ans=0,k=1,i,now,t;
    for(i=0;i<n;i++)//取出比值最大的没被访问的点。
    {
        sort(q+i,q+n,cmp);
        now=q[i];t=son(fa[now]);
        if(now==r)continue;
        ss[t]=now;ff[now]=t;
        t=farther(now);
        v[t]+=v[now];num[t]+=num[now];
    }
    while(n--)
    {
        ans+=val[r]*(k++);
        r=ss[r];
    }
    printf("%d\n",ans);
}
int main()
{
    while(input())solve();
    return 0;
}